The present invention relates to an organic-inorganic hybrid glassy material, where a raw material used in a sol-gel process is a starting material for that, and also to a process for producing the same.
With regard to materials which soften at temperatures not higher than 600° C., polymer materials, low-melting glasses, etc. have been famous and, for a long time, they have been used in many areas such as sealing and encapsulating materials, passivation glass, glaze, etc. Since their physical properties are different between polymer materials and low-melting glasses, they have been used differently depending upon the environment in which they are used. In general, in case that heat resistance and airtight property have a priority, glass has been used, while, in the field where characteristics other than heat resistance and airtight property have a priority, organic materials represented by polymer materials have been used. However, as a result of recent progress in the art, characteristics that have not been demanded up to now have received attention, and the development of materials having such characteristics has been expected.
In view of the above, the development for polymer materials where heat resistance and airtight property are enhanced and for glass where softening temperature region is made low or so-called low-melting glass has been positively carried out. Particularly in the market of electronic materials where heat resistance and airtight property are demanded, low-melting glass represented by a PbO—SiO2—B2O3 series or PbO—P2O5—SnF2 series glass has been a material which is indispensable in the field of sealing, coating, etc. of electronic parts. In addition, energy required for molding process or, in other words, the cost can be reduced in low-melting glass, as compared with high melting point glass, and therefore that meets the recent social demand for conservation of energy. Further, when it can be melted at a temperature at which an organic material having optical function property is not broken, its application as a host for (non-linear) optical material containing an optically functioning organic material to optical information communication devices such as optical switch is expected. As such, there has been a demand in many fields for materials having heat resistance and airtight property, which are characteristics of common melted glass, and also being apt to have various characteristics as in the case of polymer materials, and especially the expectation is concentrated upon low-melting glass. Furthermore, an organic-inorganic hybrid glass has been also receiving public attention as one of low-melting glasses.
With regard to low-melting glasses, for example, Tick glass represented by glass of an Sn—Pb—P—F—O type (see P. A. Tick, Physics and Chemistry of Glasses, Vol. 25, No. 6, pp. 149-154 (1984)) is famous, and, since it has a glass transition point at around 100° C. and also has an excellent water resistance, it has been used in some of the market. However, in this low-melting glass, since lead is contained in its main constituting components, there has been a necessity to use an alternative material due to the recent trend of environmental protection. In addition, demanded characteristic to Tick glass has been greatly changed, and at the same time the demand as such has been diversified as well.
With regard to common methods for the production of glass, melting method and low-temperature synthesis method have been known. Melting method is a method where a glass material is directly heated to melt and vitrified by quenching. Many kinds of glass are produced by this method, and low-melting glasses are also produced by this method. In the case of low-melting glass, however, there are many restrictions for glass composition that can be constituted such as that the containment of lead, alkali, bismuth, etc. is necessary for lowering its melting point.
On the other hand, with regard to a low-temperature synthesis method for noncrystalline bulks, there are sol-gel process, liquid-phase reaction method and nonaqueous acid-base reaction method. In a sol-gel process, a metal alkoxide or the like is subjected to a hydrolysis-polycondensation and subjected to a thermal treatment at a temperature that is higher than 500° C. (see K. Kamiya, S. Sakka and N. Tashiro, Yogyo Kyokaishi, 614-618, 84 (1976)), usually at 700 to 1,600° C., whereby a bulk can be produced. However, when the bulk produced by a sol-gel process is considered as a material for practical use, there have been many cases where the product becomes porous, due to decomposition and burning of organic materials, such as alcohol, which are introduced in the preparation of the starting solution, or due to evaporation and release, etc. in the heating process of decomposition gas of organic materials or water. Thus, there has been a problem in terms of heat resistance and airtight property. As such, in the production of bulk by a sol-gel process, many problems have been still left unsolved, and particularly production of low-melting glass by a sol-gel process has not been carried out.
Furthermore, a liquid-phase reaction method has a low productivity because of its low yield, and in addition it uses hydrofluoric acid or the like in its reaction system and is limited to the synthesis of a thin film at best. Accordingly, it is almost impossible to use it as a practical means for the synthesis of bulks.
A nonaqueous acid-base reaction method is a means which has been developed recently, and, although it is able to produce an organic-inorganic hybrid glass which is one of low-melting glasses (see M. Takahashi, H. Niida and T. Yoko, New Glass, 8-13, 17 (2002)), it is still in a stage of development and all kinds of low-melting glasses cannot be produced by that.
Accordingly, the production of many kinds of low-melting glasses has been carried out not by a low-temperature synthesis method but by a melting method. Therefore, due to melting of glass materials, the glass composition thereof is limited, and, with regard to low-melting glasses that can be produced, the type thereof has been very limited.
Incidentally, at present, low-melting glass is prominent as a material in view of heat resistance and airtight property, and it is often that the required physical property is demanded in a form of being represented by low-melting glass. However, the material is not limited to a low-melting glass. If the required physical property is satisfied, there is no large problem in low-melting or low-softening material other than glass.
JP 2005-35876 A, corresponding to US 2005/0132748 A1, discloses a process for producing an organic-inorganic hybrid glassy material, which has a softening point lower than that of low-melting glass, contains no lead, and has chemical durability, by using a phenyl-containing starting material used in sol-gel process.
In other prior art documents, there have been known a process for producing quartz glass fibers by a sol-gel process (see JP-A-62-297236), a process for producing titanium oxide fibers by a sol-gel process (see JP-A-62-223323), and a process for producing a semiconductor-doped matrix by a sol-gel process (see JP-A-1-183438). There has been also disclosed a low-melting glass of a P2O5—TeO2—ZnF2 type by a melting method (see JP-A-7-126035).